1. Field of the Invention
The present invention is broadly concerned with a relatively compact twin piston pump of the type used for pumping foods (e.g., juices of various types and particulates) during processing operations. More particularly, it is concerned with a compact pump having a number of unique features significantly reducing the cost of the pump as compared with conventional, relatively large twin piston pumps. To this end, the pump hereof includes structure for permitting quick disassembly of the pistons and sleeves to facilitate rapid cleanup, with complete elimination of expensive sleeve/piston mounting components used in conventional pumps: a specialized, jacking screw plate for permitting fine adjustment of the hydraulic cylinder assemblies used to drive the sleeves and pistons; and novel slide-plate valving arrangements adjacent the outlet of the pump which are used in lieu of expensive-to-fabricate rotary valves or the like.
2. Description of the Prior Art
Twin piston pumping devices have been in use for a number of years, particularly in the food industry in the processing of fluid and particulate materials. A particularly successful twin pump device has been commercialized by Marlen Research Corporation of Overland Park, Kansas. This pumping device is described in U.S. Pat. Nos. 4,097,962, 3,456,285, and 3,108,318. Broadly speaking, the Marlen Pump includes a pair of elongated, tubular, alternately and axially shiftable sleeves which receive corresponding pistons. The sleeves and pistons are moved through appropriate hydraulic piston and cylinder assemblies in order to effectively deliver a continuous stream of product from the pump outlet.
The standard Marlen machine employs six-inch diameter sleeves and pistons, and can develop a product output of up to about 10,000 pounds per hour, depending on the product being pumped. Such a device, by virtue of the high capacity thereof, requires somewhat specialized and expensive components. As specifically described in U.S. Pat. No. 4,097,962 (which is incorporated by reference herein), the standard Marlen Pump employs an operating and control pack comprising hydraulic power devices for the sleeves and pistons mounted on a common plate. The plate is in turn supported by a pair of rearward spherical bearings permitting precise alignment of the pack components. These bearings also allow the pack and the associated sleeve and piston assemblies to be pivoted upwardly for disassembly. The latter involves, inter alia, unthreading each piston from its associated piston rod.
The existing high capacity Marlen Pump further includes a rotatable plug valve situated in a Y-outlet conduit in order to selectively open and close the legs of the conduit to maintain continuous product flow. Such a rotary valve is an expensive part, given the need to precisely machine curved surfaces so that the valve provides adequate sealing.
As indicated above, the existing Marlen machine has proved to be highly successful in operation. Generally speaking though, certain expensive components used in the machine are justified only when a given processor can utilize the high product flow rates inherent in the Marlen machine. In the case of relatively small scale operations however, the cost of the standard Marlen machine may be in excess of what a processor may be willing to pay. It would of course be possible to downsize the standard Marlen machine to provide a lower output unit. This approach does not really deal with the problem of using the rather expensive components of the standard Marlen, however.
There is therefore a decided need in the art for a smaller, more compact twin piston pump having all of the time-proven advantages of the standard large size Marlen twin piston pump, while at the same time avoiding as much as possible the use of expensive parts found necessary and desirable in the case of the large standard machine, but which may not be required in a smaller capacity pump.